<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>清除浮动</title>
</head>
<style>
  .parent {
    border: 1px solid #000;
    overflow: hidden
  }

  .child {
    width: 100px;
    height: 100px;
    background: #eee;
    float: left;
  }
</style>

<body>
  <div class="parent">
    <div class="child"></div>
  </div>
</body>

</html>